1. Maunakea Spectroscopic Explorer (MSE), Project Design and Status
Rick Murowinski, Steve Bauman, Alan McConnachie*, Kei Szeto, Derrick Salmon, Doug Simons
Canada France Hawaii Telescope, and *National Research Council, Canada
MSE Characteristics
Telescope
- Alt-Az Prime Focus telescope with 11.25m aperture,
- M1 made of 60 x 1.44m segments
- 10m effective aperture
- 1.5 degree Wide Field Corrector and ADC
- Full performance zenith range 5 > ZA > 50 degrees,
with reduced performance to ZA=60 degrees
Enclosure
- Calotte-style, vented and thermally conditioned.
Prime Focus Instrument
- Robotic fiber positioner with 3468 elements in a
hexagonal field of 1.5 deg2
- complete field coverage with 3468 fibres to low/med R spectrograph
- complete field coverage with 1156 fibres to high R spectrograph
Low/Mid Resolution Spectrograph
spectra in (nominally) 4 units, located on the telescope structure.
- at R=3000, continuous coverage from 0.36 to 1.8 (TBC) um
- at R=6500, three spectral windows with about half wavelength coverage of LR mode.
High Resolution Spectrograph
spectra in (nominally) 2 units, located in the concrete pier beneath the telescope.
- Resolution in the range 20,000 < R < 40,000 (final value TBD)
- two spectral windows in optical range, about 40nm wide each
Schedule
- Construction Proposal Review Jan 2018
- Start of Operations Aug 2024
Model Rendering of the MSE Observatory on the Maunakea summit ridge, in place of CFHT.
Our History
The diverse and exciting scientific opportunities enabled by a wide-field, large-aperture, spectroscopic survey telescope have long been recognized by the international astronomical community. Indeed, the initial calls for such a facility appeared publically as early as The main impetus through which the MSE concept ultimately grew out of that science awareness came in 2009 through efforts led by Pat Cote at Herzberg Institute of Astrophysics (HIA, now National Research Council of Canada – Herzberg, NRC-H). Pat took the initiative to explore this niche further, to bring together scientists internationally to understand the science that could be uniquely accomplished here, and to develop the concept of a facility that would deliver the necessary capability. Their concept, one which would eventually grow into the MSE project, made use of an earlier engineering analysis by Walter Grundmann, also at HIA, showing that the CFHT piers and enclosure can accommodate both the weight and volume of a much larger telescope.
The first major effort to formally define the project was made through a Feasibility Study for a project bearing the somewhat generic and popular, but mercifully interim, moniker "next generation CFHT (ngCFHT)". The study gave us in 2012 two very important documents. One
describes the science that could be achieved with ngCFHT, as well as an analysis of the highest level requirements for ngCFHT. The second gives us a technical description of an engineering solution that is feasible, that can meet these requirements with a proposed cost and schedule. The Feasibility Study, led by Pat Cote and Kei Szeto, was funded jointly by CFHT and NRC-H.
The next milestone in the growth of the project came in early 2014, when the CFHT Board of Directors approved funding for an independent and dedicated Project Office that would develop the concepts of ngCFHT into a full Construction Proposal. The Project Office was populated with a manager, scientist and engineer and the group came together in Waikoloa Hawai'i in March for a first meeting and workshop. From Cote’s work it was clear that the scientific interest in this project was strong in many more communities than just those of the Canada, France and Hawaii partnership, and also clear that to proceed into construction the project would need funding from a wider base. In addition to the engineering development, a critical objective of the new office would need to be partnership development. To herald this project as a new observatory, reaching into an exciting future with a new partnership, the ngCFHT name was dropped and the project christened itself as the Maunakea Spectroscopic Explorer.
MSE will also re-use the surrounding building and structure supporting the dome. The current dome will be replaced with a Calotte dome with an appropriate aperture and with perhaps slightly larger (up to 8%) size.
Coverage in each window will be reduced to about half, to take advantage of the same suite of detectors.
The low-mid resolution spectrographs will certainly be constructed as a number of copies of a basic design, each unit spectrograph handling a subset of the full 3468 fiber complement. Our nominal plans are for four banks of spectrograph, each handling 867 sectra.
The high resolution spectrogram will provide a high resolution capability for up to 1156 objects per field. For stability, this spectrograph will be located in the concrete pier of the building structure.
This spectrograph will operate only in the Si response band, providing two or possibly three smaller windows of spectral coverate in the nm range. The resolution, number and width of the windows is a topic of current investigation by the MSE Science Team, and should reach a decision in the summer of For planning, we envisage the high resolution spectrograph to have a resolution of up to about 40,000 and two observing windows each with 20 to 40nm coverage.
3468 Robot Fiber Positioner
1.5 Deg Corrector and ADC
High Resolution
Spectrographs (2)
Low/Mid Resolution Spectrographs (4)
11.2m (60 segment) Primary Mirror
Low/Mid Resolution Fibre Bundle
High Resolution Fibre Bundle
Prime Focus
The single dedicated MSE instrument is a fibre-fed multi-object spectrograph, capable of gathering light from up to 3468 simultaneous objects, each being measured with spectral resolution from R=2000 to up to about R=40,000. There are three main subassemblies that make up this instrument:
1) the fibre positioner unit, 2) the fibre transmission system, and
3) the spectrographs.
We are currently studying two candidate positioner technology solutions: the tilting spine “echidna” positioner developed at AAO, and the phi-theta positioners such as that employed on LAMOST among other projects. Important characteristics being investigated during the conceptual design study include how complete the coverage of science objects per field in the different high resolution and low resolution multiplex requirements, and the stability and repeatability of spectral data resulting from each technology.
Spectrographs
MSE will employ two spectrograph systems. One, for low and medium resolution observations, will be located on the telescope structure so that fibre lengths are as short as possible. The second, for high resolution observations, will be in the stable concrete pier beneath the telescope.
The low-mid resolution spectrograph will provide coverage over the science waveband from 0.36 to 1.8um (TBC, the ability to deliver H band coverage is under investigation at this time). In the R=3000 low resolution mode, it will provide continuous coverage over the waveband using CCD and HgCd/Te infrared detectors. In the R=6500 medium resolution mode, the
Development on Maunakea
MSE will be the first major facility to take advantage of the provisions in the 2009 Mauna Kea Comprehensive Management Plan for re-development of an existing facility. The objective of this class of project is to return the performance of existing facilities to the world-class science that originally justified their construction, done in partnership with regulators and the local community to ensure the values of the Mauna are not degraded in any way. While the objectives are clear, the process a project would need to follow is less so at this time. We are looking forward to increased clarity into the process emerging, as the currently tense situation on development upon Maunakea settles and the terms for a new UH Master Lease come to light.
The MSE Observatory
The project’s grand vision is to provide a facility that will deliver the wealth and quality of observational data needed to answer the next generation of questions about our universe, and to build this facility with no impact on the environment of Maunakea and the Big Island of Hawai’i – indeed, we intend to complete this project bringing a net benefit to our local community, as well as a crucial new facility to the international science community.
Central themes in our construction plans are those of recycling wherever we can during the development of MSE, and minimizing the consumption of resources during operations. MSE will use the same building and pier that CFHT telescope now sits upon, and although it will be necessary to replace the dome with one with a larger opening for our larger telescope, once the project is completed the new facility will be almost indistinguishable to the local community from the current CFHT, while to the astronomical community it will be a completely new and vibrant facility. MSE will build upon CFHT’s pioneering work in remote operation, with no staff at all travelling to the summit at night. We're working to reduce the amount of daytime maintenance activity needed, as well. Since MSE will only perform one single task (and perform it very well), there will no longer be campaigns for instrument changes at the telescope. With smaller living space at the telescope, water consumption (much of it being used for humidifiers) will also reduce.
Canada France Hawaii Telescope
Maunakea Spectroscope Explorer
The Telescope and Enclosure
CFHT, built in the 1970’s, is a general use telescope with 3.6 meter primary mirror on an equatorial mount. Typical of its day, the telescope primary mirror is “slow”: the curvature is shallow and the focal point is a long distance from the mirror.
Together, these conditions require a larger dome to move around within than more modern, optically “fast” telescopes on altitude-azimuth mounts. In fact the dome on CFHT is even larger and heavier than the telescope needs, perhaps a monument to when steel was cheaper and engineering calculations were performed conservatively by hand. We will replace the CFHT telescope with a modern alt-az segmented-mirror telescope, with m segments making a primary mirror of 11.25m in diameter (10m effective aperture after aperture blockage is taken into account), sitting atop the current concrete pier and delivering a 1.5 degree diameter corrected field to the fiber positioner unit.
Viewed from the outside, whether at sea level or on the Mauna, MSE will appear virtually unchanged from the familiar CFHT observatory.
MSE Design-Phase Collaboration